In a hydraulic damper used for a vehicle such as passenger vehicles, trucks, motorcycles, etc. bump stop rubber etc. is conventionally and generally used in order to prevent the components from abutting on each other in a compressed state of the dumper.
For example, a cushion device is disclosed in which at least one of the mutually abutting surfaces of the bump stop rubber or the bump stopper is provided with concaves and convexes in order to attenuate impacts on the damper by making the bump stop rubber and the bump stopper abut on each other when the damper is compressed to the maximum level (see FIG. 1 of Patent Document 1 for example)
FIG. 1 shows an example of a conventional configuration that uses a bump stop rubber as described above in a hydraulic damper. The hydraulic damper shown in FIG. 1 includes an upper mount 1 for fixing the hydraulic damper to the vehicle body, an upper spring sheet 2 disposed below the upper mount 1, a piston rod 3 fixed in such a manner that it can swing with respect to the upper mount 1 and the upper spring sheet 2, a cylinder 5 having an oil chamber 4, etc.
The hydraulic damper shown in FIG. 1 further includes a piston valve 6 that partitions the oil chamber 4 in the cylinder 5 into oil chambers 4a and 4b, an outer cylinder 7 that covers the outer periphery of the cylinder 5, and a bump stopper 8 which has the piston rod 3 inserted into its center hole and whose outer peripheral portion is fit into the upper end portion of the outer cylinder 7 so as to be fixed on it.
Further, bump stop rubber 9 that is fit with the piston rod 3 outside of the piston rod 3 is set between the bump stopper 8 and the upper spring sheet 2. The bump stop rubber 9 is configured by using an elastic member such as for example resin etc.
When a load is applied to a hydraulic damper to compress it, i.e., when the piston rod 3 has been pushed by the cylinder 5 as represented by arrow a, the bump stop rubber 9 functions as a cushion to prevent a situation where the upper spring sheet 2 and the bump stopper 8 directly abut on each other.
Patent Document 1 described above aims to attenuate impacts applied to a damper more effectively when the damper is compressed to the maximum level, by providing at least one of the mutually abutting surfaces of the bump stop rubber or the bump stopper with concaves and convexes in a cushion unit as described above.